Bohr’s theory of atomic structure is based on Planck’s quantum theory of radiation. The basic postulates are;
- An electron is an atom that revolves around the nucleus in a specific circular path called the orbit.
These orbits are also called energy shells or energy levels because electrons in each orbit have definite energy and are at a fixed distance from the nucleus. These orbits are denoted by 1,2,3 etc (or K, L, M, N etc).
2. As long as an electron revolves in a particular orbit, it neither absorbs nor emits energy.
An electron does not radiate energy if it stays in one orbit and therefore does not slow down. The energy of an electron in each orbit remains the same.
3. When an electron moves from one orbit to another orbit it either absorbs or emits energy.
When an electron move toward the nucleus energy is radiated/emitted and if it is moved away from the nucleus, energy is absorbed. That is an electron can move from one energy level to another by quantum or photon jump only.
4. The electron can move only in that orbit in which the angular momentum (mvr) of the revolving electron is an integral multiple of h/2π. i.e= nh/2π